While life expectancy has increased for the U.S. as a whole, wealthy people have seen the greatest gains in life expectancy, recent government research has shown.

The gap in life expectancy between richer and poorer Americans "mirrored trends in infant mortality and in death from heart disease and certain cancers," according to the New York Times.

Gopal Singh, a demographer at the Department of Health and Human Services, was one of the researchers involved in the study. Federal officials found "'widening socioeconomic inequalities in life expectancy' at birth and at every age level," Singh said, according to the New York Times.

People in the most affluent group of Americans could expect to live 75.8 years and people in the poorest group could expect to live 73 years in 1980 to 1982, according to Singh. That's a difference of 2.8 years. "By 1998-2000, the difference in life expectancy had increased to 4.5 years (79.2 versus 74.7 years), and it continues to grow, he said" according to the New York Times.

Also of note is that the "life expectancy was higher for the most affluent in 1980 than for the most deprived group in 2000," Singh said, according to the New York Times.

With the rising costs of health care, it's not too surprising that those who can afford it are living longer than those who can't.